diff --git a/src/pg/sql/30_dot_density.sql b/src/pg/sql/30_dot_density.sql
index 8b7f81b..e5c4f81 100644
--- a/src/pg/sql/30_dot_density.sql
+++ b/src/pg/sql/30_dot_density.sql
@@ -11,8 +11,8 @@
 --
 -- Returns: Multipoint with the requested points
 
-CREATE OR REPLACE FUNCTION CDB_DotDensity(g geometry, no_points integer, max_iter integer DEFAULT 1000)
- RETURNS SETOF geometry
+CREATE OR REPLACE FUNCTION CDB_DotDensity(g geometry(Polygon, 4326), no_points integer, max_iter integer DEFAULT 1000)
+ RETURNS SETOF geometry(Point, 4326)
 AS $$
  DECLARE
      extent GEOMETRY;